The exhaust gas laws that regulate pollutant emissions of self-igniting internal combustion engines are constantly becoming more stringent. In addition, newly developed engine management systems of internal combustion engines are subject to the requirement that they ensure low fuel consumption and longer lifespan. The optimization of the combustion in the combustion chamber of a self-igniting internal combustion engine is achieved through the use of controlled fuel injection. For this purpose, in an engine control unit based on a combustion chamber pressure signal, a pressure sensor is used that has to meet very high demands with regard to the achievable degree of reliability of the measurement precision, as well as an optimized combustion chamber.
Kraftfahrtechnisches Taschenbuch [Automotive Handbook], 23rd ed., Braunschweig; Wiesbaden, Vieweg 1999, ISBN 3-528-03876-4, page 111, describes an integrated silicon combustion chamber pressure sensor. The silicon combustion chamber pressure sensor includes a transmitting tappet, a silicon platform that is used for the introduction of force, and an integrated silicon pressure sensor. On one side of the steel assembly plate, there are situated one or more terminal pins, from which a connecting line runs to the integrated silicon pressure sensor. According to this system, the silicon chip is not immediately exposed to the high temperatures in a combustion chamber of an internal combustion engine. This is achieved using a metallic separating diaphragm, as well as a sufficiently long tappet for force transmission. Through the micromechanical attachment of a platform in the center of the diaphragm, the silicon chip is made into a force sensor. The pressure forces received by the front diaphragm are introduced into the sensor chip made of silicon via the tappet, with only slight adulteration by the platform. Said sensor chip is situated in an assembly position that is set back, and is thus exposed only to operating temperatures less than 150° C.
International Application WO 97/31251 A describes a combustion chamber pressure sensor for determining engine knock and misfires. A fiber-optic combustion chamber pressure sensor is integrated into a spark plug. This sensor is configured in such a way that the spark plug body is penetrated by a conductor. A diaphragm formed as a key having a nonuniform thickness reduces the mechanical stress acting on the diaphragm and increases the reliability of the sensor. Excess pressures acting on the combustion chamber pressure sensor are reduced through bent sections formed on the diaphragm.
International Application WO 01/53556 A1 describes a spring steel of the maraging type is known. This is a high-tensile, hardenable, corrosion-resistant spring steel made up essentially of 6.0 to 9.0% by weight Ni, 11.0 to 15.0% by weight Cr, 0.1 to 0.3% by weight Ti, and 0.2 to 0.3% by weight Be, the remainder being Fe, and whose martensite temperature Ms is ≧130° C., and having a ferrite content CFerrite<3%. In this high-tensile hardenable corrosion-resistant spring steel, up to 50% of the nickel content may be replaced by cobalt. Also, up to 35% of the chromium content may be replaced by molybdenum and/or tungsten.
A type of measurement device, currently widely available, for acquiring the combustion chamber pressure in the combustion chamber of an internal combustion engine is called a “stand-alone ” sensor, for whose use a separate bore is provided in the cylinder head wall. Generally, the price of such sensors is fairly high, but this is regarded as justified by the high degree of measurement precision that can be achieved. For series production use in the automotive field, however, only comparatively low-cost pressure sensors make sense from the economic point of view. The integration of sensors into already-existing components of the cylinder head of an internal combustion engine achieves a significant price advantage, and in this way makes large-scale series production use possible. In cylinder heads of modern internal combustion engines, no additional bores are to be made, because the space conditions, in particular in four-valve internal combustion engines, are extremely restricted, and the course of coolant ducts is fixedly predetermined, causing the space in the cylinder head of an internal combustion engine to be extremely restricted.